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PCRE Functions
PHP Manual

preg_split

(PHP 4, PHP 5)

preg_split — Split string by a regular expression

Description

array preg_split ( string $pattern , string $subject [, int $limit = -1 [, int $flags = 0 ]] )

Split the given string by a regular expression.

Parameters

pattern

The pattern to search for, as a string.

subject

The input string.

limit

If specified, then only substrings up to limit are returned with the rest of the string being placed in the last substring. A limit of -1, 0 or null means "no limit" and, as is standard across PHP, you can use null to skip to the flags parameter.

flags

flags can be any combination of the following flags (combined with the | bitwise operator):

PREG_SPLIT_NO_EMPTY
If this flag is set, only non-empty pieces will be returned by preg_split().
PREG_SPLIT_DELIM_CAPTURE
If this flag is set, parenthesized expression in the delimiter pattern will be captured and returned as well.
PREG_SPLIT_OFFSET_CAPTURE

If this flag is set, for every occurring match the appendant string offset will also be returned. Note that this changes the return value in an array where every element is an array consisting of the matched string at offset 0 and its string offset into subject at offset 1.

Return Values

Returns an array containing substrings of subject split along boundaries matched by pattern.

Changelog

Version Description
4.3.0 The PREG_SPLIT_OFFSET_CAPTURE was added
4.0.5 The PREG_SPLIT_DELIM_CAPTURE was added

Examples

Example #1 preg_split() example : Get the parts of a search string

<?php
// split the phrase by any number of commas or space characters,
// which include " ", \r, \t, \n and \f
$keywords = preg_split("/[\s,]+/", "hypertext language, programming");
?>

Example #2 Splitting a string into component characters

<?php
$str = 'string';
$chars = preg_split('//', $str, -1, PREG_SPLIT_NO_EMPTY);
print_r($chars);
?>

Example #3 Splitting a string into matches and their offsets

<?php
$str = 'hypertext language programming';
$chars = preg_split('/ /', $str, -1, PREG_SPLIT_OFFSET_CAPTURE);
print_r($chars);
?>

The above example will output:

Array
(
    [0] => Array
        (
            [0] => hypertext
            [1] => 0
        )

    [1] => Array
        (
            [0] => language
            [1] => 10
        )

    [2] => Array
        (
            [0] => programming
            [1] => 19
        )

)

Notes

Tip

If you don't need the power of regular expressions, you can choose faster (albeit simpler) alternatives like explode() or str_split().

See Also

  • spliti() - Split string into array by regular expression case insensitive
  • split() - Split string into array by regular expression
  • implode() - Join array elements with a string
  • preg_match() - Perform a regular expression match
  • preg_match_all() - Perform a global regular expression match
  • preg_replace() - Perform a regular expression search and replace
  • preg_last_error() - Returns the error code of the last PCRE regex execution

PCRE Functions
PHP Manual
User Contributed Notes
preg_split
sergei dot garrison at gmail dot com
05-Mar-2010 04:04
If you need to split a list of "tags" while allowing for user error, you'll find this more useful than the manual's first example.

<?php
$string = 'one, two,three,     four  , five,six seven';
 $array = preg_split("/[\s]*[,][\s]*/", $string);
 print_r($array);
 // Array ( [0] => one [1] => two [2] => three [3] => four [4] => five [5] => six seven )
 ?>

This splits the string *only* by commas, regardless of how many spaces there are on either side of any comma.
nesbert at gmail dot com
28-Jan-2010 11:46
Hope this helps someone...

<?php
 /**
 * Split a string into groups of words with a line no longer than $max
 * characters.
 *
 * @param string $string
 * @param integer $max
 * @return array
 **/
 function split_words($string, $max = 1)
{
    $words = preg_split('/\s/', $string);
    $lines = array();
    $line = '';
   
    foreach ($words as $k => $word) {
        $length = strlen($line . ' ' . $word);
        if ($length <= $max) {
            $line .= ' ' . $word;
        } else if ($length > $max) {
            if (!empty($line)) $lines[] = trim($line);
            $line = $word;
        } else {
            $lines[] = trim($line) . ' ' . $word;
            $line = '';
        }
    }
    $lines[] = ($line = trim($line)) ? $line : $word;

    return $lines;
}
 ?>
jan dot sochor at icebolt dot info
24-Oct-2009 10:26
Sometimes PREG_SPLIT_DELIM_CAPTURE does strange results.

<?php
$content = '<strong>Lorem ipsum dolor</strong> sit <img src="test.png" />amet <span class="test" style="color:red">consec<i>tet</i>uer</span>.';
 $chars = preg_split('/<[^>]*[^\/]>/i', $content, -1, PREG_SPLIT_NO_EMPTY | PREG_SPLIT_DELIM_CAPTURE);
 print_r($chars);
 ?>
 Produces:
Array
(
    [0] => Lorem ipsum dolor
    [1] =>  sit <img src="test.png" />amet
    [2] => consec
    [3] => tet
    [4] => uer
)

So that the delimiter patterns are missing. If you wanna get these patters remember to use parentheses.

<?php
$chars = preg_split('/(<[^>]*[^\/]>)/i', $content, -1, PREG_SPLIT_NO_EMPTY | PREG_SPLIT_DELIM_CAPTURE);
 print_r($chars); //parentheses added
 ?>
 Produces:
Array
(
    [0] => <strong>
    [1] => Lorem ipsum dolor
    [2] => </strong>
    [3] =>  sit <img src="test.png" />amet
    [4] => <span class="test" style="color:red">
    [5] => consec
    [6] => <i>
    [7] => tet
    [8] => </i>
    [9] => uer
    [10] => </span>
    [11] => .
)
php at dmi dot me dot uk
06-Oct-2009 08:23
To split a camel-cased string using preg_split() with lookaheads and lookbehinds:

<?php
 function splitCamelCase($str) {
  return preg_split('/(?<=\\w)(?=[A-Z])/', $str);
}
 ?>
Peter -the pete- de Pijd
24-Sep-2009 09:34
If you want to use something like explode(PHP_EOL, $string) but for all combinations of \r and \n, try this one:

<?php
$text = "A\nB\rC\r\nD\r\rE\n\nF";
 $texts = preg_split("/((\r(?!\n))|((?<!\r)\n)|(\r\n))/", $text);
 ?>

result:
array("A", "B", "C", "D", "", "E", "", "F");
buzoganylaszlo at yahoo dot com
01-Aug-2009 07:57
Extending m.timmermans's solution, you can use the following code as a search expression parser:

<?php
$search_expression = "apple bear \"Tom Cruise\" or 'Mickey Mouse' another word";
 $words = preg_split("/[\s,]*\\\"([^\\\"]+)\\\"[\s,]*|" . "[\s,]*'([^']+)'[\s,]*|" . "[\s,]+/", $search_expression, 0, PREG_SPLIT_NO_EMPTY | PREG_SPLIT_DELIM_CAPTURE);
 print_r($words);
 ?>

The result will be:
Array
(
    [0] => apple
    [1] => bear
    [2] => Tom Cruise
    [3] => or
    [4] => Mickey Mouse
    [5] => another
    [6] => word
)

1. Accepted delimiters: white spaces (space, tab, new line etc.) and commas.

2. You can use either simple (') or double (") quotes for expressions which contains more than one word.
wf
28-May-2009 04:36
Spacing out your CamelCase using preg_replace:

<?php

 function spacify($camel, $glue = ' ') {
    return preg_replace( '/([a-z0-9])([A-Z])/', "$1$glue$2", $camel );
}

echo spacify('CamelCaseWords'), "\n"; // 'Camel Case Words'
 echo spacify('camelCaseWords'), "\n"; // 'camel Case Words'

 ?>
chris AT cmbuckley DOT co DOT uk
27-May-2009 10:11
Here's a helpful function to space out your CamelCase using preg_split:

<?php

 function spacify($camel, $glue = ' ') {
    return $camel[0] . substr(implode($glue, array_map('implode', array_chunk(preg_split('/([A-Z])/',
        ucfirst($camel), -1, PREG_SPLIT_NO_EMPTY | PREG_SPLIT_DELIM_CAPTURE), 2))), 1);
}

echo spacify('CamelCaseWords'); // 'Camel Case Words'
 echo spacify('camelCaseWords'); // 'camel Case Words'

 ?>
kenorb at gmail dot com
23-May-2009 02:56
If you need convert function arguments without default default values and references, you can try this code:

<?php
    $func_args = '$node, $op, $a3 = NULL, $form = array(), $a4 = NULL'
    $call_arg = preg_match_all('@(?<func_arg>\$[^,= ]+)@i', $func_args, $matches);
    $call_arg = implode(',', $matches['func_arg']);
 ?>
 Result: string = "$node,$op,$a3,$form,$a4"
bit_kahuna at yahoo dot com
27-Mar-2009 07:02
how to display a shortened text string with an elipsis, but on word boundaries only.

<?php
 function truncate($string, $max = 70, $rep = '...') {

    $words = preg_split("/[\s]+/", $string);
   
    $newstring = '';
    $numwords = 0;
   
    foreach ($words as $word) {
        if ((strlen($newstring) + 1 + strlen($word)) < $max) {
            $newstring .= ' '.$word;
            ++$numwords;
        } else {
            break;
        }
    }

    if ($numwords < count($words)) {
        $newstring .= $rep;
    }
   
    return $newstring;
}
 ?>

hope this helps someone!  thanks for all the help from everyone else!!
csaba at alum dot mit dot edu
17-Mar-2009 09:06
If the task is too complicated for preg_split, preg_match_all might come in handy, since preg_split is essentially a special case.

I wanted to split a string on a certain character (asterisk), but only if it wasn't escaped (by a preceding backslash).  Thus, I should ensure an even number of backslashes before any asterisk meant as a splitter.  Look-behind in a regular expression wouldn't work since the length of the preceding backslash sequence can't be fixed.  So I turned to preg_match_all:

<?php
 // split a string at unescaped asterisks
// where backslash is the escape character
 $splitter = "/\\*((?:[^\\\\*]|\\\\.)*)/";
 preg_match_all($splitter, "*$string", $aPieces, PREG_PATTERN_ORDER);
 $aPieces = $aPieces[1];

 // $aPieces now contains the exploded string
// and unescaping can be safely done on each piece
 foreach ($aPieces as $idx=>$piece)
  $aPieces[$idx] = preg_replace("/\\\\(.)/s", "$1", $piece);
 ?>
anajilly
17-Jul-2008 08:17
<?php
$s = '<p>bleh blah</p><p style="one">one two three</p>';

 $htmlbits = preg_split('/(<p( style="[-:a-z0-9 ]+")?>|<\/p>)/i', $s, -1, PREG_SPLIT_DELIM_CAPTURE);

 print_r($htmlbits);
 ?>

Array
(
    [0] =>
    [1] => <p>
    [2] => bleh blah
    [3] => </p>
    [4] =>
    [5] => <p style="one">
    [6] =>  style="one"
    [7] => one two three
    [8] => </p>
    [9] =>
)

two interesting bits:

1. When using PREG_SPLIT_DELIM_CAPTURE, if you use more than one pair of parentheses, the result array can have members representing all pairs.  See array indexes 5 and 6 to see two adjacent delimiter results in which the second is a subset match of the first.

2. If a parenthesised sub-expression is made optional by a following question mark (ex: '/abc (optional subregex)?/') some split delimiters may be captured in the result while others are not.  See array indexes 1 and 2 to see an instance where the overall match succeeded and returned a delimiter while the optional sub-expression '( style="[-:a-z0-9 ]+")?' did not match, and did not return a delimiter.  This means it's possible to have a result with an unpredictable number of delimiters in the result array.

This second aspect is true irrespective of the number of pairs of parentheses in the regex.  This means: in a regular expression with a single optional parenthesised sub-expression, the overall expression can match without generating a corresponding delimiter in the result.
m dot timmermans at home dot NOSPAM dot nl
29-May-2008 10:56
For people who want to use the double quote to group words/fields, kind of like CSV does, you can use the following expression:
<?php
$keywords = preg_split( "/[\s,]*\\\"([^\\\"]+)\\\"[\s,]*|[\s,]+/", "textline with, commas and \"quoted text\" inserted", 0, PREG_SPLIT_DELIM_CAPTURE );
 ?>
 Which will result in:
Array
(
    [0] => textline
    [1] => with
    [2] => commas
    [3] => and
    [4] => quoted text
    [5] => inserted
)
crispytwo at yahoo dot com
04-Sep-2007 08:29
I was having trouble getting the PREG_SPLIT_DELIM_CAPTURE flag to work because I missed reading the "parenthesized expression" in the documentation :-( 

So the pattern should look like:
/(A)/
not just
/A/
and it works as described/expected.
Steve
23-Mar-2005 04:41
preg_split() behaves differently from perl's split() if the string ends with a delimiter. This perl snippet will print 5:

my @a = split(/ /, "a b c d e ");
print scalar @a;

The corresponding php code prints 6:

<?php print count(preg_split("/ /", "a b c d e ")); ?>

This is not necessarily a bug (nowhere does the documentation say that preg_split() behaves the same as perl's split()) but it might surprise perl programmers.
jetsoft at iinet.net.au
25-Sep-2004 03:01
To clarify the "limit" parameter and the PREG_SPLIT_DELIM_CAPTURE option,

<?php
$preg_split('(/ /)', '1 2 3 4 5 6 7 8', 4 ,PREG_SPLIT_DELIM_CAPTURE );
 ?>

returns:

('1', ' ', '2', ' ' , '3', ' ', '4 5 6 7 8')

So you actually get 7 array items not 4
dave at codewhore dot org
29-May-2002 07:01
The above description for PREG_SPLIT_OFFSET_CAPTURE may be a bit confusing.

When the flag is or'd into the 'flags' parameter of preg_split, each match is returned in the form of a two-element array. For each of the two-element arrays, the first element is the matched string, while the second is the match's zero-based offset in the input string.

For example, if you called preg_split like this:

preg_split('/foo/', 'matchfoomatch', -1, PREG_SPLIT_OFFSET_CAPTURE);

it would return an array of the form:

Array(
  [0] => Array([0] => "match", [1] => 0),
  [1] => Array([1] => "match", [1] => 8)
)

Note that or'ing in PREG_DELIM_CAPTURE along with PREG_SPLIT_OFFSET_CAPTURE works as well.
 

 
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